Update runner to latest version (removed built-in C++ model files).

The runner project has also been updated to test the filter and
model outputs, but none of those files should end up in the
extension either.

README.md

@@ -70,11 +70,6 @@ file:
 #define MESSAGE_BUS_LISTENER_URGENT                 0x0080
 ```
 
-### Built-in ML model
-
-The `MLRUNNER_USE_EXAMPLE_MODEL` flag can be configured as described in:
-https://github.com/microbit-foundation/pxt-microbit-ml-runner#built-in-ml-model
-
 ### Debug messages
 
 To enable debug print from this extension, add the following into your

pxt.json

@@ -4,7 +4,7 @@
     "description": "Machine learning extension to support micro:bit CreateAI",
     "dependencies": {
         "core": "*",
-        "machine-learning-runner": "github:microbit-foundation/pxt-microbit-ml-runner#v0.4.6"
+        "machine-learning-runner": "github:microbit-foundation/pxt-microbit-ml-runner#v0.4.8"
     },
     "files": [
         "README.md",